Conventional fans have the purpose of moving a substance of gaseous state. A multiple number of blades fixed rigidly to the hub and surrounded by a ring produce airflow when rotating. The usual problems with fans, especially of large size, are (1) axial deflection (2) the stress level under centrifugal loading. Axial deflection of the fan is undesirable for reasons of interference with other components as well as for aerodynamic and aeroacoustic reasons. High blade stresses can lead to catastrophic failure of the fan. In typical configurations, to add strength to the fan, the chord length is increased to fix the blade tip to a surrounding ring that joins the blade tips. These configurations add material to the outermost radial sections of the blade in order to achieve increased strength. However, the added mass contributes to excessive axial deflection.
There is a need to provide a fan that minimizes deflection and maximizes strength by eliminating high stresses at critical areas and that combines efficient aerodynamic and aeroacoustic performance with the structural performance.